Heat resistant UV blocking coatings are known in the art. For example, see U.S. Pat. No. 5,480,722 and 2002/0122962A1.
Cerium oxide has been combined with silica or titania in an attempt to enhance the quality of the film layer. While the addition of silica may lower the refractive index of the coating, the addition of titania may further increase the index of refraction and may also enhance the UV blocking ability of the cerium oxide coating. When thin films of ceria-titania-silica are formed on glass substrates rainbow-like colours may be seen. The rainbow-like colours may be caused by interference of light caused, at least in part, by a large difference between refractive indices of substrate and coating.
In addition, such ceria-titania-silica coatings tend to be highly reflective, which may not be desired in window applications. In order to suppress these potentially undesired effects, multi-layer oxide coatings of varying index have been reported in literature. Application of multiple oxide layers, however, is generally not very attractive for commercial applications because of the complexity of manufacturing processes and associated higher yield losses.
The interference effects of high refractive index ceria-titania coatings may be minimized in some instances by increasing the coating thickness. Thicker coatings, however, tend to be not only undesirably yellow but also highly reflective. By increasing the content of low index silica, the refractive index of the ceria-titania-silica coatings may be sufficiently reduced and the reflection and interference effects of coating can be minimized.
Because the molar extinction coefficients of ceria and ceria-titania are not high enough in the UV region, however, the dilution effect caused by adding higher levels of silica typically requires thicker coatings to achieve adequate UV blocking. Generally, the thicker the coating, the more likely it is to develop micro cracks during heat treatment process.
Thus there may exist a need for heat treatable UV blocking coatings that comprise a single layer oxide coating of lower refractive index, which remain substantially crack-free after high temperature heat treatment and/or which are largely free of undesired optical effects and also are cost effective to manufacture.
In at least certain example embodiments of this invention, it may be an object to provide a method to produce heat treatable coatings of lower oxide compositions that can block UV radiation effectively without exhibiting undesired optical defects. In at least certain example embodiments of this invention, it may be an object to provide a method to produce thicker heat treatable coatings that remain substantially crack-free after high temperature heat treatment. In at least certain example embodiments of this invention, it is may be an object to provide a method that incorporates application of a heat resistant organic polymer over coating on the top of oxide-precursor base coating which pyrolyzes completely during heat treatment processes while facilitating formation of thicker substantially crack-free coatings.
The term “substantially crack-free” does not imply the absence of all cracks; rather, it means that to the extent that any cracks form in the coating during production, the cracks (if any) do not substantially interfere with the overall structure, function, and operation of the UV coating, either alone or in the layered stack.
In certain example embodiments of this invention, there exists a need in the art for more efficient coating capable of blocking significant amounts of UV or IR and UV radiation. In certain example embodiments, a heat resistant coating is provided that may be processed (e.g., thermally tempered) cost effectively with minimal steps.
In certain example embodiments of this invention, there is provided a method of making a coated article including a UV blocking coating, the method comprising: applying a first wet coating comprising titanium, cerium, and silicon on the glass substrate, and at least partially curing the first wet coating solution to form a UV blocking coating on the glass substrate, the UV blocking coating comprising a mixture of oxides of cerium, titanium, and silicon and having a refractive index (n) of from about 1.55 to 1.85.
In certain example embodiments of this invention, there is provided a method of making a coated article, the method comprising: optionally forming a low-E coating on a glass substrate, the low-E coating comprising at least one infrared (IR) reflecting layer located between at least first and second dielectric layers; applying a first wet coating comprising a silane and cerium on the glass substrate; at least partially curing the wet coating to form a UV blocking coating on the glass substrate, the UV blocking coating comprising a mixture of oxides of silicon and cerium, and optionally titanium; applying a second wet coating comprising a photomonomer and/or photopolymer on the glass substrate over the UV blocking coating; and curing the second wet coating though exposure to radiation.
In certain example embodiments of this invention, there is provided a coated article comprising: a glass substrate; a UV blocking coating provided on the glass substrate over at least the glass substrate for blocking at least some UV radiation passing through the coated article; and an organic polymer top coating provided on the glass substrate over at least the UV blocking coating, the organic polymer being formed by curing a photomonomer and/or photopolymer through exposure to radiation.
In certain example embodiments of this invention, there is provided a method of making a coated article, the method comprising: forming a low-E coating on a glass substrate, the low-E coating comprising at least one infrared (IR) reflecting layer located between at least first and second dielectric layers; applying a wet coating comprising at least one UV blocking oxide and/or at least one precursor of a UV blocking oxide on the glass substrate over the low-E coating; forming a UV blocking and IR blocking coating on the glass substrate; forming an organic polymer top coating on the glass substrate; and subjecting the coated glass substrate to a heat treatment process including temperatures of at least about 400 degrees C.